How long must you run a test to catch a 1% watch-time lift?
Power & sample sizeHardProblem. Leadership wants to ship a Reels change if it lifts watch time by at least 1%. How do you decide how big and how long the experiment must be, and what if 1% is below what you can detect?
Before you reveal: say your answer out loud, as if you were in the real interview — get your reasoning across clearly first. There is no single correct answer: reading what the interviewer is really after and defending your own thinking is what makes an answer strong.